OkHttpClient client = new OkHttpClient.Builder()
    .addInterceptor(new LoggingInterceptor())
    .build();

Request request = new Request.Builder()
    .url("http://www.publicobject.com/helloworld.txt")
    .header("User-Agent", "OkHttp Example")
    .build();

Response response = client.newCall(request).execute();
response.body().close();
```

    assertFailsWith<NullPointerException> {
      (mapOf("User-Agent" to null) as Map<String, String>).toHeaders()
    }
  }

  @Test fun toMultimapGroupsHeaders() {
    val headers =
      Headers.headersOf(
        "cache-control",
        "no-cache",
        "cache-control",
        "no-store",
        "user-agent",
        "OkHttp",
      )
    val headerMap = headers.toMultimap()

User-agent: FessCrawler
Disallow:           # allows all 

User-agent: BruteBot
Disallow: /
Allow: /foo/bar/
Crawl-delay: 1314000

# welcome!
User-agent: Googlebot
Crawl-delay: 1

User-agent: *
Disallow: /private/
Disallow: /help        # disallows /help.html, /help/index.html, etc.
Allow: /help/faq.html
Crawl-delay: 3

User-agent: Crawler
Disallow: /aaa

User-agent: Crawler/1.0
Disallow: /bbb

 * </ul>
 *
 * @author bowez
 * @author shinsuke
 *
 */
public class RobotsTxtHelper {

    /** Pattern for parsing user-agent records. */
    protected static final Pattern USER_AGENT_RECORD =
            Pattern.compile("^user-agent:\\s*([^\\t\\n\\x0B\\f\\r]+)\\s*$", Pattern.CASE_INSENSITIVE);

    /** Pattern for parsing disallow records. */

from typing import Union

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(user_agent: Union[str, None] = Header(default=None)):

	}
}

// uaTransport - User-Agent  transport
type uaTransport struct {
	ua string
	rt http.RoundTripper
}

func (u *uaTransport) RoundTrip(req *http.Request) (*http.Response, error) {
	req2 := req.Clone(req.Context())
	req2.Header.Set("User-Agent", u.ua)
	return u.rt.RoundTrip(req2)
}

// WithUserAgent wraps an existing transport with custom User-Agent

        this.authSchemeProviderMap = authSchemeProviderMap;
    }

    /**
     * Sets the user agent string.
     * @param userAgent The user agent string.
     */
    public void setUserAgent(final String userAgent) {
        this.userAgent = userAgent;
    }

    /**
     * Sets the credentials provider.

 *  Fix: Include a backwards-compatible `OkHttp-Response-Source` header with
    `OkUrlFactory `responses.
 *  Fix: Don't include a default User-Agent header in requests made with the Call
    API. Requests made with OkUrlFactory will continue to have a default user
    agent.
 *  New: Guava-like API to create headers:

    ```java
    Headers headers = Headers.of(name1, value1, name2, value2, ...).
    ```

import okhttp3.internal.EmptyTags

class RequestCommonTest {
  @Test
  fun constructorNormal() {
    val url = "https://example.com/".toHttpUrl()
    val body = "hello".toRequestBody()
    val headers = headersOf("User-Agent", "RequestTest")
    val method = "PUT"
    val request =
      Request(
        url = url,
        headers = headers,
        method = method,
        body = body,
      )

            logger.debug("replace: {} -> {}", url, newUrl);
        }
        return newUrl;
    }

    /**
     * Checks if the user agent matches the path mapping.
     *
     * @param pathMapping the path mapping
     * @return true if the user agent matches
     */
    protected boolean matchUserAgent(final PathMapping pathMapping) {
        if (!pathMapping.hasUAMathcer()) {
            return true;